The present invention is directed to granulating machines for the size reduction of plastic material and particularly to a knife construction therefor. Devices of this nature often by the combined action of rotor weight, speed etc., impart large forces upon relatively small segments of plastic material in contact with the blade, rotor and housing portions of such granulators.
In some cases these forces are large enough to liquify portions of the thermoplastic plastic material being worked. This leads to the forcing of this liquified plastic into the interface between the knife itself and the knife seat area of the rotor, which undesirably leads to a buildup of solidified plastic underneath the knife structure resulting in its improper positioning vis-a-vis the rotor and other granulator portions. This tendency has been found especially true in knives having blade portions of the hook-shaped or similar configuration which present an undercut or pocket for receipt of curls, chips and the like of plastic material cut from a larger piece. The forward interface or junction between the blade and the rotor, with hook-shaped blades is located within such undercut or pocket area and particularly accessible to such liquified plastic.
It is accordingly a primary object of the present invention to provide a knife construction having a configuration so as to prevent plastic material liquified by the granulated cutting action to enter between the interface of the knife and its rotor seat.
A further object of the present invention is the provision of a granulator knife construction which applies an unusually high degree of pressure at the forward parting line between the knife and the rotor seat upon which it is adapted to rest so as to seal such cooperating surfaces and thus prevent plastic liquified by the granulating action to enter into such interface areas.
Still another object of the present invention is the provision of a rotor construction including a seat adapted for the receipt of a granulating knife which presents an enlarged forward surface so as to distribute force applied by plastic liquified by the granulating action over a larger than normal surface so as to reduce the force or tendency for such to enter between the knife and rotor seat interface.
A still further object of the present invention is the provision of a combination rotor knife construction in which the rotor includes an upstanding pad for receipt of a hook-shaped blade having an undercut segment wherein the stepped portion of the pad forms a continuation of such blade segment.
A further object of the invention is the provision of a modified knife construction which can be utilized without modifying existing rotors so as to provide a higher and accordingly effective sealing relationship between the front face of the blade and the rotor seat.
These and other objects of the invention as will become apparent from the foregoing description are accomplished by the provision of a granulator knife so constructed for operative association with a granulator rotor having a plurality of cut out portions in the outer periphery thereof to form blade receiving seats. The knife includes a base portion adapted to engage such seats, which base portion includes a relatively narrow downwardly extending foot disposed at the forward edge thereof and forming a continuation of an undercut blade segment adapted to receive plastic material and means in the top surface of the knife for receiving a plurality of bolts so as to force said foot into high pressure sealing relationship engagement with the rotor seat, thus effectively preventing the flow of liquefied plastic material between the knife/rotor seat interface. Additionally the rotor seat may be provided with an upwardly stepped configuration wherein the front face in turn forms a continuation of the above described plastic receiving blade undercut or pocket and accordingly serves to increase the area in which the force applied by such liquid plastic is distributed.
Other objects and features of the invention will become more apparent by reference to the following drawing and detailed description of the invention.